Display (display) devices in various modes depending on materials and characteristics, such as liquid crystal devices (LCD), organic light-emitting diodes (OLED: organic electroluminescence (EL)), are used in televisions and in mobile phones. Furthermore, in recent years, electronic paper (ePaper) devices for electronic books adopting a microcapsule system, an electrophoresis system, or the like have been used. Furthermore, by using a material with high transparency, a transparent OLED and a transparent electronic paper are being developed.
Since electronic paper performs display through reflected light and OLED performs display through spontaneous light emission, the property difference between the devices themselves appears as their characteristic differences. Generally, while OLED shows high performance in brightness, gradation, color development, and response speed, electronic paper is superior in power consumption and visibility under external light. Furthermore, OLED has a risk of aging due to burn-in.
With such a background, Patent Literature 1 describes a proposal in which a transparent OLED on the front side and an electronic paper on the backside serve as display layers.